When Val Diamond made her debut in "Beach Blanket Babylon" in January 1979, she was a singing envelope. Legs and face showing, no arms. In another number she was a singing waitress wearing a huge Coca-Cola on her head.

Initially, she wasn't sure if a silly revue with spine-crushing hats was her metier. "I thought I was too hip for it," she says. "Too hip to be wearing stupid costumes onstage. I was a serious musician and a serious actress. I wanted to do Shakespeare; that's where I thought I'd be. Whoa!"

Thirty years later - she celebrates her anniversary Jan. 17, following the 9:30 p.m. performance - Diamond is a San Francisco institution. A long-distance runner sans pareil. A symbol of San Francisco tenacity, oddness and cheer.

Just don't ask Diamond how many performances she's given. "I don't know," she answers. "I really don't know." Simple math tells us that Diamond - after 30 years of eight shows per week, roughly 48 weeks per year - has logged somewhere in the neighborhood of 11,500 performances.

That's more than Carol Channing in "Hello, Dolly!" More than Yul Brynner in "The King and I." More than the two of them combined. More, probably, than any other American performer in a currently running show.

Even so, Diamond says she's never wearied of her "Beach Blanket Bingo" gig. Ever since Steve Silver created the show in the mid-'70s, Diamond says, it's been in constant mutation and rebirth. "Constantly. If something happens in the news, it's in. It'll be in here the day it happens."

Over the years she's played Alexis Carrington Colby, the Joan Collins character from "Dynasty"; a Singing Nun who sang "Dominique" and then stripped down to become Gidget; a tap-dancing Gandhi; the queen of England; a biker chick belting "Total Eclipse of the Heart"; a Jewish mother; Marie Antoinette; and her favorite, a French whore.

The material changes, but the "Beach Blanket" format and the zany, clever-kids-gone-wild spirit remains intact. Same with the show's production values. "They've kept it really low-tech," Diamond says, "because there's no room to expand. No place to fly the sets or props. Nothing's mechanized.

"The sound system is much better than it was. The hats aren't nearly as heavy. But really, it's the same show. Just a little faster-paced now."

Diamond, 57, is sitting in the living room of the cozy Sonoma home she shares with her husband of 21 years, "Beach Blanket" trumpet player Steve Salgo (himself the veteran of 9,000 performances). The furniture is plush but not showy. A Christmas tree dominates one corner, and throughout the house are pieces, some whimsical, some classic, that Diamond inherited after her parents died: ceramic angels, a chandelier.

Diamond and Salgo moved here 15 years ago and commute five or six days per week, 44 miles in each direction in their Prius. She says it's no big deal. "I usually fall asleep in the car."

Keeping it real

Unlike some entertainers, Diamond hasn't turned her home into a shrine to herself. There are three framed "Beach Blanket" photos in the hallway, modestly hung, one from the 1983 Davies Symphony Hall performance for Queen Elizabeth II. Otherwise, there's a clear division here between Diamond the institution and Diamond the homemaker.

An excellent cook, Diamond has prepared salad and chicken soup topped with ravioli. She serves lunch in her cheerful dining room with its canary-yellow walls, a skylight and collections of Italian crockery. Classical music is playing in the adjacent den, the same room where Diamond watches movies. Sci-fi is her favorite.

Unlike some comics, who in real life are glum and overly serious, Diamond is cheerful. She's also innately funny. As she carries two soup bowls from the kitchen to the dining room - taking little duck steps, making a pantomime of trying not to spill the soup - she brings to mind a silent-film comedian.

A range of silly expressions cross her face as she speaks: eyes bugged, a single eyebrow raised, conspiratorial winks. The same mannerisms, largely, that she makes each night at Club Fugazi. Carol Burnett was her primary influence, Diamond says, and when she first starting doing double takes in the show, "I realized I was totally channeling Jack Benny."

Funny beginnings

Diamond grew up in Castro Valley, when the town was full of chicken farms and kids climbed fences and roamed at will. In grade school, she started to emerge as the class clown - a total surprise to her Jewish dad, Harold, and Italian immigrant mother, Lilly. Neither of them was so inclined.

Despite her musical chops - she still does a solo act apart from "Beach Blanket" - Diamond identifies more as an actor than singer. In high school, she played the title role in "Medea" and Anna in "The King and I."

"I only started singing, honestly, because more people came to the musicals than the plays. It was all about, 'Well I want to perform for more people. So I better learn how to sing.' "

After high school, Diamond toured the country for eight years with a pop-rock band, playing casinos and halls and the usual hovels. Burned out by the road, in 1978 she auditioned for "Beach Blanket Babylon," at the urging of her friend Shelley Werk, one of the show's original cast members. Silver liked her and gave her the job - over the objections of the dance captain.

"I didn't look like most of the people who were in the show. I was heavyset and I think that bothered them 'cause there was a lot of dancing for me. But I can dance. Women that aren't Twiggy-thin can still dance."

Silver's presence

Diamond was extremely close to Silver and shared his dedication to merriment. She still hasn't recovered from his death from AIDS in June 1995, she says, and suspects she never will.

Losing him was "horrible, really horrible. At that point, my husband and I didn't know if we could go on, because my husband had gotten very close to Steve as well. But we just sort of did it. And for a while, every night while singing 'San Francisco' I'd be crying.

"I think of him every night. You feel him still in the theater. You look up at the balcony and you feel like he's still there."

People constantly ask when Diamond will leave the show. She has a ready answer, upbeat and pragmatic, but underneath it you can feel the sense of dread and overwhelming sadness at her inevitable departure.

"The audiences keep me fresh," she says. "If they faded away, that would make me think twice. But to play for big, huge houses every night of laughing people; that's what it's all about."

"If I feel like I'm not performing well, if I feel like people aren't enjoying me anymore, then that definitely would be time for me to say, 'OK, hang it up.' But I still think there's a lot of life in me."